This invention relates to machines for driving spikes through holes in rail tie plates to secure rails to ties.
It is obviously important to locate the tie plate holes accurately and ensure that the spikes are driven accurately through the holes. Various types of sensing devices are available for locating the holes, such as tactile sensors or electro-optical sensors but a problem encountered by all is that it is physically impossible to locate the hole sensor and the drive head at exactly the same position on the machine and so when the sensor locates a hole it is then necessary to move the drive head an appropriate distance so that it becomes positioned over the hole.
Usually a spike setter is provided for setting a spike under the drive head, and this too has to be moved the appropriate distance over the hole.